<!DOCTYPE html>
<html lang="zh-ch">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    body {
      padding: 20px;
    }

    input {
      -webkit-appearance: none;
      background-color: #fff;
      background-image: none;
      border-radius: 4px;
      border: 1px solid #dcdfe6;
      box-sizing: border-box;
      color: #606266;
      display: inline-block;
      font-size: inherit;
      height: 30px;
      line-height: 30px;
      outline: none;
      padding: 0 15px;
      transition: border-color .2s cubic-bezier(.645, .045, .355, 1);
      /* width: 100%; */
      cursor: pointer;
    }

    input:hover {
      border-color: #c0c4cc;
    }

    input:focus {
      outline: none;
      border-color: #409eff;
    }
    ::-webkit-input-placeholder{
      color: #c0c4cc;
      font-size: 14px;
    }

    button {}
  </style>
</head>

<body>
  <div>
    <input type="text" placeholder="请输入内容">
    <button>提交</button>
  </div>
</body>

</html>